/*
 * contrib/btree_gist/btree_utils_var.c
 */
#include "postgres.h"

#include "btree_gist.h"

#include <math.h>
#include <limits.h>
#include <float.h>

#include "btree_utils_var.h"
#include "utils/pg_locale.h"
#include "utils/builtins.h"
#include "utils/rel.h"

/* used for key sorting */
typedef struct
{
    int            i;
    GBT_VARKEY *t;
} Vsrt;

typedef struct
{
    const gbtree_vinfo *tinfo;
    Oid            collation;
    FmgrInfo   *flinfo;
} gbt_vsrt_arg;


PG_FUNCTION_INFO_V1(gbt_var_decompress);
PG_FUNCTION_INFO_V1(gbt_var_fetch);


Datum
gbt_var_decompress(PG_FUNCTION_ARGS)
{
    GISTENTRY  *entry = (GISTENTRY *) PG_GETARG_POINTER(0);
    GBT_VARKEY *key = (GBT_VARKEY *) DatumGetPointer(PG_DETOAST_DATUM(entry->key));

    if (key != (GBT_VARKEY *) DatumGetPointer(entry->key))
    {
        GISTENTRY  *retval = (GISTENTRY *) palloc(sizeof(GISTENTRY));

        gistentryinit(*retval, PointerGetDatum(key),
                      entry->rel, entry->page,
                      entry->offset, FALSE);

        PG_RETURN_POINTER(retval);
    }

    PG_RETURN_POINTER(entry);
}

/* Returns a better readable representation of variable key ( sets pointer ) */
GBT_VARKEY_R
gbt_var_key_readable(const GBT_VARKEY *k)
{
    GBT_VARKEY_R r;

    r.lower = (bytea *) &(((char *) k)[VARHDRSZ]);
    if (VARSIZE(k) > (VARHDRSZ + (VARSIZE(r.lower))))
        r.upper = (bytea *) &(((char *) k)[VARHDRSZ + INTALIGN(VARSIZE(r.lower))]);
    else
        r.upper = r.lower;
    return r;
}


/*
 * Create a leaf-entry to store in the index, from a single Datum.
 */
static GBT_VARKEY *
gbt_var_key_from_datum(const struct varlena *u)
{
    int32        lowersize = VARSIZE(u);
    GBT_VARKEY *r;

    r = (GBT_VARKEY *) palloc(lowersize + VARHDRSZ);
    memcpy(VARDATA(r), u, lowersize);
    SET_VARSIZE(r, lowersize + VARHDRSZ);

    return r;
}

/*
 * Create an entry to store in the index, from lower and upper bound.
 */
GBT_VARKEY *
gbt_var_key_copy(const GBT_VARKEY_R *u)
{
    int32        lowersize = VARSIZE(u->lower);
    int32        uppersize = VARSIZE(u->upper);
    GBT_VARKEY *r;

    r = (GBT_VARKEY *) palloc0(INTALIGN(lowersize) + uppersize + VARHDRSZ);
    memcpy(VARDATA(r), u->lower, lowersize);
    memcpy(VARDATA(r) + INTALIGN(lowersize), u->upper, uppersize);
    SET_VARSIZE(r, INTALIGN(lowersize) + uppersize + VARHDRSZ);

    return r;
}


static GBT_VARKEY *
gbt_var_leaf2node(GBT_VARKEY *leaf, const gbtree_vinfo *tinfo, FmgrInfo *flinfo)
{
    GBT_VARKEY *out = leaf;

    if (tinfo->f_l2n)
        out = (*tinfo->f_l2n) (leaf, flinfo);

    return out;
}


/*
 * returns the common prefix length of a node key
*/
static int32
gbt_var_node_cp_len(const GBT_VARKEY *node, const gbtree_vinfo *tinfo)
{
    GBT_VARKEY_R r = gbt_var_key_readable(node);
    int32        i = 0;
    int32        l = 0;
    int32        t1len = VARSIZE(r.lower) - VARHDRSZ;
    int32        t2len = VARSIZE(r.upper) - VARHDRSZ;
    int32        ml = Min(t1len, t2len);
    char       *p1 = VARDATA(r.lower);
    char       *p2 = VARDATA(r.upper);

    if (ml == 0)
        return 0;

    while (i < ml)
    {
        if (tinfo->eml > 1 && l == 0)
        {
            if ((l = pg_mblen(p1)) != pg_mblen(p2))
            {
                return i;
            }
        }
        if (*p1 != *p2)
        {
            if (tinfo->eml > 1)
            {
                return (i - l + 1);
            }
            else
            {
                return i;
            }
        }

        p1++;
        p2++;
        l--;
        i++;
    }
    return (ml);                /* lower == upper */
}


/*
 * returns true, if query matches prefix ( common prefix )
 */
static bool
gbt_bytea_pf_match(const bytea *pf, const bytea *query, const gbtree_vinfo *tinfo)
{
    bool        out = FALSE;
    int32        qlen = VARSIZE(query) - VARHDRSZ;
    int32        nlen = VARSIZE(pf) - VARHDRSZ;

    if (nlen <= qlen)
    {
        char       *q = VARDATA(query);
        char       *n = VARDATA(pf);

        out = (memcmp(q, n, nlen) == 0);
    }

    return out;
}


/*
 * returns true, if query matches node using common prefix
 */
static bool
gbt_var_node_pf_match(const GBT_VARKEY_R *node, const bytea *query, const gbtree_vinfo *tinfo)
{
    return (tinfo->trnc && (
                            gbt_bytea_pf_match(node->lower, query, tinfo) ||
                            gbt_bytea_pf_match(node->upper, query, tinfo)
                            ));
}


/*
*  truncates / compresses the node key
*  cpf_length .. common prefix length
*/
static GBT_VARKEY *
gbt_var_node_truncate(const GBT_VARKEY *node, int32 cpf_length, const gbtree_vinfo *tinfo)
{
    GBT_VARKEY *out = NULL;
    GBT_VARKEY_R r = gbt_var_key_readable(node);
    int32        len1 = VARSIZE(r.lower) - VARHDRSZ;
    int32        len2 = VARSIZE(r.upper) - VARHDRSZ;
    int32        si;
    char       *out2;

    len1 = Min(len1, (cpf_length + 1));
    len2 = Min(len2, (cpf_length + 1));

    si = 2 * VARHDRSZ + INTALIGN(len1 + VARHDRSZ) + len2;
    out = (GBT_VARKEY *) palloc0(si);
    SET_VARSIZE(out, si);

    memcpy(VARDATA(out), r.lower, len1 + VARHDRSZ);
    SET_VARSIZE(VARDATA(out), len1 + VARHDRSZ);

    out2 = VARDATA(out) + INTALIGN(len1 + VARHDRSZ);
    memcpy(out2, r.upper, len2 + VARHDRSZ);
    SET_VARSIZE(out2, len2 + VARHDRSZ);

    return out;
}



void
gbt_var_bin_union(Datum *u, GBT_VARKEY *e, Oid collation,
                  const gbtree_vinfo *tinfo, FmgrInfo *flinfo)
{
    GBT_VARKEY_R eo = gbt_var_key_readable(e);
    GBT_VARKEY_R nr;

    if (eo.lower == eo.upper)    /* leaf */
    {
        GBT_VARKEY *tmp;

        tmp = gbt_var_leaf2node(e, tinfo, flinfo);
        if (tmp != e)
            eo = gbt_var_key_readable(tmp);
    }

    if (DatumGetPointer(*u))
    {
        GBT_VARKEY_R ro = gbt_var_key_readable((GBT_VARKEY *) DatumGetPointer(*u));
        bool        update = false;

        nr.lower = ro.lower;
        nr.upper = ro.upper;

        if ((*tinfo->f_cmp) (ro.lower, eo.lower, collation, flinfo) > 0)
        {
            nr.lower = eo.lower;
            update = true;
        }

        if ((*tinfo->f_cmp) (ro.upper, eo.upper, collation, flinfo) < 0)
        {
            nr.upper = eo.upper;
            update = true;
        }

        if (update)
            *u = PointerGetDatum(gbt_var_key_copy(&nr));
    }
    else
    {
        nr.lower = eo.lower;
        nr.upper = eo.upper;
        *u = PointerGetDatum(gbt_var_key_copy(&nr));
    }
}


GISTENTRY *
gbt_var_compress(GISTENTRY *entry, const gbtree_vinfo *tinfo)
{
    GISTENTRY  *retval;

    if (entry->leafkey)
    {
        struct varlena *leaf = PG_DETOAST_DATUM(entry->key);
        GBT_VARKEY *r;

        r = gbt_var_key_from_datum(leaf);

        retval = palloc(sizeof(GISTENTRY));
        gistentryinit(*retval, PointerGetDatum(r),
                      entry->rel, entry->page,
                      entry->offset, TRUE);
    }
    else
        retval = entry;

    return (retval);
}


Datum
gbt_var_fetch(PG_FUNCTION_ARGS)
{
    GISTENTRY  *entry = (GISTENTRY *) PG_GETARG_POINTER(0);
    GBT_VARKEY *key = (GBT_VARKEY *) DatumGetPointer(PG_DETOAST_DATUM(entry->key));
    GBT_VARKEY_R r = gbt_var_key_readable(key);
    GISTENTRY  *retval;

    retval = palloc(sizeof(GISTENTRY));
    gistentryinit(*retval, PointerGetDatum(r.lower),
                  entry->rel, entry->page,
                  entry->offset, TRUE);

    PG_RETURN_POINTER(retval);
}


GBT_VARKEY *
gbt_var_union(const GistEntryVector *entryvec, int32 *size, Oid collation,
              const gbtree_vinfo *tinfo, FmgrInfo *flinfo)
{
    int            i = 0,
                numranges = entryvec->n;
    GBT_VARKEY *cur;
    Datum        out;
    GBT_VARKEY_R rk;

    *size = sizeof(GBT_VARKEY);

    cur = (GBT_VARKEY *) DatumGetPointer(entryvec->vector[0].key);
    rk = gbt_var_key_readable(cur);
    out = PointerGetDatum(gbt_var_key_copy(&rk));

    for (i = 1; i < numranges; i++)
    {
        cur = (GBT_VARKEY *) DatumGetPointer(entryvec->vector[i].key);
        gbt_var_bin_union(&out, cur, collation, tinfo, flinfo);
    }


    /* Truncate (=compress) key */
    if (tinfo->trnc)
    {
        int32        plen;
        GBT_VARKEY *trc = NULL;

        plen = gbt_var_node_cp_len((GBT_VARKEY *) DatumGetPointer(out), tinfo);
        trc = gbt_var_node_truncate((GBT_VARKEY *) DatumGetPointer(out), plen + 1, tinfo);

        out = PointerGetDatum(trc);
    }

    return ((GBT_VARKEY *) DatumGetPointer(out));
}


bool
gbt_var_same(Datum d1, Datum d2, Oid collation,
             const gbtree_vinfo *tinfo, FmgrInfo *flinfo)
{
    GBT_VARKEY *t1 = (GBT_VARKEY *) DatumGetPointer(d1);
    GBT_VARKEY *t2 = (GBT_VARKEY *) DatumGetPointer(d2);
    GBT_VARKEY_R r1,
                r2;

    r1 = gbt_var_key_readable(t1);
    r2 = gbt_var_key_readable(t2);

    return ((*tinfo->f_cmp) (r1.lower, r2.lower, collation, flinfo) == 0 &&
            (*tinfo->f_cmp) (r1.upper, r2.upper, collation, flinfo) == 0);
}


float *
gbt_var_penalty(float *res, const GISTENTRY *o, const GISTENTRY *n,
                Oid collation, const gbtree_vinfo *tinfo, FmgrInfo *flinfo)
{
    GBT_VARKEY *orge = (GBT_VARKEY *) DatumGetPointer(o->key);
    GBT_VARKEY *newe = (GBT_VARKEY *) DatumGetPointer(n->key);
    GBT_VARKEY_R ok,
                nk;

    *res = 0.0;

    nk = gbt_var_key_readable(newe);
    if (nk.lower == nk.upper)    /* leaf */
    {
        GBT_VARKEY *tmp;

        tmp = gbt_var_leaf2node(newe, tinfo, flinfo);
        if (tmp != newe)
            nk = gbt_var_key_readable(tmp);
    }
    ok = gbt_var_key_readable(orge);

    if ((VARSIZE(ok.lower) - VARHDRSZ) == 0 && (VARSIZE(ok.upper) - VARHDRSZ) == 0)
        *res = 0.0;
    else if (!(((*tinfo->f_cmp) (nk.lower, ok.lower, collation, flinfo) >= 0 ||
                gbt_bytea_pf_match(ok.lower, nk.lower, tinfo)) &&
               ((*tinfo->f_cmp) (nk.upper, ok.upper, collation, flinfo) <= 0 ||
                gbt_bytea_pf_match(ok.upper, nk.upper, tinfo))))
    {
        Datum        d = PointerGetDatum(0);
        double        dres;
        int32        ol,
                    ul;

        gbt_var_bin_union(&d, orge, collation, tinfo, flinfo);
        ol = gbt_var_node_cp_len((GBT_VARKEY *) DatumGetPointer(d), tinfo);
        gbt_var_bin_union(&d, newe, collation, tinfo, flinfo);
        ul = gbt_var_node_cp_len((GBT_VARKEY *) DatumGetPointer(d), tinfo);

        if (ul < ol)
        {
            dres = (ol - ul);    /* reduction of common prefix len */
        }
        else
        {
            GBT_VARKEY_R uk = gbt_var_key_readable((GBT_VARKEY *) DatumGetPointer(d));
            unsigned char tmp[4];

            tmp[0] = (unsigned char) (((VARSIZE(ok.lower) - VARHDRSZ) <= ul) ? 0 : (VARDATA(ok.lower)[ul]));
            tmp[1] = (unsigned char) (((VARSIZE(uk.lower) - VARHDRSZ) <= ul) ? 0 : (VARDATA(uk.lower)[ul]));
            tmp[2] = (unsigned char) (((VARSIZE(ok.upper) - VARHDRSZ) <= ul) ? 0 : (VARDATA(ok.upper)[ul]));
            tmp[3] = (unsigned char) (((VARSIZE(uk.upper) - VARHDRSZ) <= ul) ? 0 : (VARDATA(uk.upper)[ul]));
            dres = Abs(tmp[0] - tmp[1]) + Abs(tmp[3] - tmp[2]);
            dres /= 256.0;
        }

        *res += FLT_MIN;
        *res += (float) (dres / ((double) (ol + 1)));
        *res *= (FLT_MAX / (o->rel->rd_att->natts + 1));
    }

    return res;
}


static int
gbt_vsrt_cmp(const void *a, const void *b, void *arg)
{
    GBT_VARKEY_R ar = gbt_var_key_readable(((const Vsrt *) a)->t);
    GBT_VARKEY_R br = gbt_var_key_readable(((const Vsrt *) b)->t);
    const gbt_vsrt_arg *varg = (const gbt_vsrt_arg *) arg;
    int            res;

    res = (*varg->tinfo->f_cmp) (ar.lower, br.lower, varg->collation, varg->flinfo);
    if (res == 0)
        return (*varg->tinfo->f_cmp) (ar.upper, br.upper, varg->collation, varg->flinfo);

    return res;
}

GIST_SPLITVEC *
gbt_var_picksplit(const GistEntryVector *entryvec, GIST_SPLITVEC *v,
                  Oid collation, const gbtree_vinfo *tinfo, FmgrInfo *flinfo)
{
    OffsetNumber i,
                maxoff = entryvec->n - 1;
    Vsrt       *arr;
    int            svcntr = 0,
                nbytes;
    char       *cur;
    GBT_VARKEY **sv = NULL;
    gbt_vsrt_arg varg;

    arr = (Vsrt *) palloc((maxoff + 1) * sizeof(Vsrt));
    nbytes = (maxoff + 2) * sizeof(OffsetNumber);
    v->spl_left = (OffsetNumber *) palloc(nbytes);
    v->spl_right = (OffsetNumber *) palloc(nbytes);
    v->spl_ldatum = PointerGetDatum(0);
    v->spl_rdatum = PointerGetDatum(0);
    v->spl_nleft = 0;
    v->spl_nright = 0;

    sv = palloc(sizeof(bytea *) * (maxoff + 1));

    /* Sort entries */

    for (i = FirstOffsetNumber; i <= maxoff; i = OffsetNumberNext(i))
    {
        GBT_VARKEY_R ro;

        cur = (char *) DatumGetPointer(entryvec->vector[i].key);
        ro = gbt_var_key_readable((GBT_VARKEY *) cur);
        if (ro.lower == ro.upper)    /* leaf */
        {
            sv[svcntr] = gbt_var_leaf2node((GBT_VARKEY *) cur, tinfo, flinfo);
            arr[i].t = sv[svcntr];
            if (sv[svcntr] != (GBT_VARKEY *) cur)
                svcntr++;
        }
        else
            arr[i].t = (GBT_VARKEY *) cur;
        arr[i].i = i;
    }

    /* sort */
    varg.tinfo = tinfo;
    varg.collation = collation;
    varg.flinfo = flinfo;
    qsort_arg((void *) &arr[FirstOffsetNumber],
              maxoff - FirstOffsetNumber + 1,
              sizeof(Vsrt),
              gbt_vsrt_cmp,
              (void *) &varg);

    /* We do simply create two parts */

    for (i = FirstOffsetNumber; i <= maxoff; i = OffsetNumberNext(i))
    {
        if (i <= (maxoff - FirstOffsetNumber + 1) / 2)
        {
            gbt_var_bin_union(&v->spl_ldatum, arr[i].t, collation, tinfo, flinfo);
            v->spl_left[v->spl_nleft] = arr[i].i;
            v->spl_nleft++;
        }
        else
        {
            gbt_var_bin_union(&v->spl_rdatum, arr[i].t, collation, tinfo, flinfo);
            v->spl_right[v->spl_nright] = arr[i].i;
            v->spl_nright++;
        }
    }

    /* Truncate (=compress) key */
    if (tinfo->trnc)
    {
        int32        ll = gbt_var_node_cp_len((GBT_VARKEY *) DatumGetPointer(v->spl_ldatum), tinfo);
        int32        lr = gbt_var_node_cp_len((GBT_VARKEY *) DatumGetPointer(v->spl_rdatum), tinfo);
        GBT_VARKEY *dl;
        GBT_VARKEY *dr;

        ll = Max(ll, lr);
        ll++;

        dl = gbt_var_node_truncate((GBT_VARKEY *) DatumGetPointer(v->spl_ldatum), ll, tinfo);
        dr = gbt_var_node_truncate((GBT_VARKEY *) DatumGetPointer(v->spl_rdatum), ll, tinfo);
        v->spl_ldatum = PointerGetDatum(dl);
        v->spl_rdatum = PointerGetDatum(dr);
    }

    return v;
}


/*
 * The GiST consistent method
 */
bool
gbt_var_consistent(GBT_VARKEY_R *key,
                   const void *query,
                   StrategyNumber strategy,
                   Oid collation,
                   bool is_leaf,
                   const gbtree_vinfo *tinfo,
                   FmgrInfo *flinfo)
{
    bool        retval = FALSE;

    switch (strategy)
    {
        case BTLessEqualStrategyNumber:
            if (is_leaf)
                retval = (*tinfo->f_ge) (query, key->lower, collation, flinfo);
            else
                retval = (*tinfo->f_cmp) (query, key->lower, collation, flinfo) >= 0
                    || gbt_var_node_pf_match(key, query, tinfo);
            break;
        case BTLessStrategyNumber:
            if (is_leaf)
                retval = (*tinfo->f_gt) (query, key->lower, collation, flinfo);
            else
                retval = (*tinfo->f_cmp) (query, key->lower, collation, flinfo) >= 0
                    || gbt_var_node_pf_match(key, query, tinfo);
            break;
        case BTEqualStrategyNumber:
            if (is_leaf)
                retval = (*tinfo->f_eq) (query, key->lower, collation, flinfo);
            else
                retval =
                    ((*tinfo->f_cmp) (key->lower, query, collation, flinfo) <= 0 &&
                     (*tinfo->f_cmp) (query, key->upper, collation, flinfo) <= 0) ||
                    gbt_var_node_pf_match(key, query, tinfo);
            break;
        case BTGreaterStrategyNumber:
            if (is_leaf)
                retval = (*tinfo->f_lt) (query, key->upper, collation, flinfo);
            else
                retval = (*tinfo->f_cmp) (query, key->upper, collation, flinfo) <= 0
                    || gbt_var_node_pf_match(key, query, tinfo);
            break;
        case BTGreaterEqualStrategyNumber:
            if (is_leaf)
                retval = (*tinfo->f_le) (query, key->upper, collation, flinfo);
            else
                retval = (*tinfo->f_cmp) (query, key->upper, collation, flinfo) <= 0
                    || gbt_var_node_pf_match(key, query, tinfo);
            break;
        case BtreeGistNotEqualStrategyNumber:
            retval = !((*tinfo->f_eq) (query, key->lower, collation, flinfo) &&
                       (*tinfo->f_eq) (query, key->upper, collation, flinfo));
            break;
        default:
            retval = FALSE;
    }

    return retval;
}
